All that info is good. Yes, 300 Blk is finicky when you start varying from the DI, 16" barrel with supers.
I had an ok write up on this that I posted on 300 Blk but that site is down ATM for some reason...
My last built and test points that I can remember ATM:
Weapon specs:
300 Blk, 8.5" Hbar, pistol gas, AA piston kit with XLP block and light BC with POF roller cam pin, Mil Spec lower, buffer tube, Silencerco Omega when suppressed.
Ammo Specs:
1. Super - Off the shelf, Bulk SAA, 147 gn FMJ, MV of 1750-1850 fps actual.
2. Super - 150 gn Sierra FMJBT GK, 20.5 gn of A1680, Fed SR 205 primer, COL 2.140"
3. Super - 150 gn Nosler, BST, 20.5 gn of A1680, Fed SR 205 primer, COL 2.150"
4. Sub - 220 gn Nosler, CC, 11.5 gn of A1680, Fed SR 205 primer, COL 2.260" - MV of 1026 fps
5. Sub - 220 gn Nosler, CC, 11.5 gn of A1680, Fed SR 205 primer, COL 2.230" - MV of 1058.6 fps
(Ammo testing specs: ambient temp - 65-68F at ALT 3675' ASL.)
Testing was done with focus on BCG lock back and fired by a human (not in a test fixture)
Points of modification:
Piston Drive Rod gap tolerance -.020" to .015" (although nominal as I didn't see much difference between .015" and .020")
Buffer to -H (no internal weights)
Buffer Spring - carbine spring with 3.5" removed. To get clinical you will need to measure spring rates. Wolff springs are an option and so are Tubbs. standard is 11lbs in battery and 13.5lbs compressed.
I did not have my rate gauge available when I chopped my spring so I had to guess and use POE in .5" increments. Keep in mind that you are changing the overall rate by cutting. Generally springs get stiffer when cut. Spring science definitely plays a part and there are many factors that I won't dive into here.
I am in the process of producing a factory spring with a 300 bulk piston rate for both Subs and Super fire.
Drive Rod Spring - can be changed with spring of different rate. Ace hardware. (AA did not recommend this change)
Gas Port to .125"
Gas Block - port opened at south by 30 degrees and polished for flow and alignment.
"With these types of set ups I would suggest having spare, wear parts such as springs as modded items are usually not as resilient."
Conclusion:
Depending on my specific load all Supers locked back at half gas both suppressed and unsurpassed. Recoil was not overly forceful.
Most Sub loads locked back with suppressed fire and full gas. Some sub loads failed to lock back but still stroked enough to strip and chamber the next round.
Mag/load testing is still on going as subs with large C.O.A.L.s put the bullet tips uncomfortably close to the inside of the mag and many hang up once more than 10 rounds are loaded.
hope this helps by giving some reference points.
DK